Reproduction device, recording method and playback method

ABSTRACT

An AV Clip formed by multiplexing a video stream and a graphics stream and recorded on a BD-ROM as a recording medium. The video stream constitutes a moving picture while the graphics stream enables graphics to be overlaid on the moving picture, and includes pieces of control information called a PCS and an ICS. When the AV Clip is played back immediately following playback of another digital stream, the control information indicates to the reproduction device that the presence of data already in memory of a graphics decoder is to be continuous.

TECHNICAL FIELD

The present invention relates to seamless playback, and morespecifically to improvements in consumer reproduction devices andrecording media which support GUI technology. Typical examples of suchrecording media are BD-ROM (Blu-ray Disc Read Only Memory) andDVD-video.

BACKGROUND ART

Seamless playback is used when playing back a plurality of digitalstreams to eliminate interruptions that occur when switching from onedigital stream to the next. Multi-story movies in which the plot changesin response to user operations or device status (e.g. a rating levelsetting) are produced using seamless playback technology. There arecurrently many in the movie business who would like to make use of thistechnology to add value to their products and boost the share price oftheir company.

Each digital stream includes a video stream constituting a movingpicture, an audio stream constituting sound, and elementary streams ofvarious types, including a graphics stream constituting subtitles andmenus. The above streams are multiplexed to form the digital stream.Technology that enables seamless playback of video streams multiplexedinto a plurality of digital streams is disclosed in the patent documents1 and 2.

-   Patent Document 1: International publication WO97/13367-   Patent Document 2: International publication WO97/13363

DISCLOSURE OF THE PRESENT INVENTION Problems the Present Invention Aimsto Solve

When a movie is composed of a plurality of digital streams, each streammay be played back independently or immediately following anotherdigital stream as part of a sequence. In conventional DVD reproductiondevices, an internally provided video decoder (for decoding video streamdata) makes a clear distinction between independent playback andplayback immediately following another digital stream. In the latter,the conventional DVD reproduction device is able to realize seamlessplayback of the video stream by ensuring that the presence of data inmemory in the video decoder is continuous. In an internally providedgraphics decoder (for decoding graphics stream data), on the other hand,memory holding the graphics stream data is all cleared when switchingfrom one digital stream to another. When the video streams are beingplayed back seamlessly a given graphics stream may not be independent ofthe graphics stream in a preceding digital stream. However, even if thegraphics streams are not independent, the graphics stored in thereproduction device will be cleared at the switch-over from one digitalstream to another. As a result, momentary interruptions in the displayof subtitles and menus occur at the switch-over.

Owing to the momentary interruptions that occur in the display ofsubtitles and menus, an author must expend time and effort selectingappropriate points at which to place digital stream boundaries. Theboundaries may be chosen to include scenes without any lines and othersections where no subtitles or graphics appear. Thus, when a movie isbeing split into a plurality of digital streams using conventionaltechnology, there is a problem in that the author is constrained toselect portions not including speech as points for placing digitalstream boundaries.

Consequently, when making multi-story type movies, it is oftenimpossible to realize playback in accordance with the desired storyline.

The object of the present invention is to provide a recording mediumthat reduces constraints on the selection of boundaries and therebysimplifies the production of movies having a number of playback paths.

Means to Solve the Problem

In order to achieve the above object, the recording medium of thepresent invention is a recording medium having recorded thereon one ormore digital streams each generated by multiplexing a video stream and agraphics stream, wherein the video stream constitutes a moving picture,the graphics stream constitutes graphics to be overlaid on the movingpicture, and includes status information, and if the digital stream isto be played back by a reproduction device immediately following anotherdigital stream, the status information indicates that presence ofmanagement data already in memory for graphics display is to becontinuous.

Effects of the Present Invention

According to the above construction, the status information instructsthe reproduction device to continue memory management at the playbackswitch-over from a preceding digital stream to an immediately followingdigital stream. Consequently, the reproduction device does not reset thegraphics decoder when playback switches between the digital streams.Having menu management continue makes it possible to select a portion atwhich menus or subtitles are displayed at a digital stream boundary.This reduces constraints on the selection of points for placingboundaries between digital streams, and in the case of a multi-storytype movie, enables playback that follows a desired storyline.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a use of a recording medium of the present invention;

FIG. 2 shows an application layer format of a BD-ROM expressed using adirectory structure;

FIG. 3 shows a schematic structure of an AV clip;

FIG. 4A shows a structure of a presentation graphics stream;

FIG. 4B shows PES packets obtained by converting functional segments;

FIG. 5 shows a logical structure made up of functional segments ofvarious types;

FIG. 6 shows a playback time axis of an AV Clip to which a DSn isallocated;

FIG. 7A shows a data structure of an ODS;

FIG. 7B shows a data structure of a PDS;

FIG. 8A shows a data structure of a WDS;

FIG. 8B shows a data structure of a PCS;

FIG. 9 illustrates an example of how subtitles are realized;

FIG. 10 shows an example of a PCS in a DS1;

FIG. 11 shows an example of a PCS in a DS2;

FIG. 12 shows a playback time axis of an AV Clip to which a DSn isallocated;

FIG. 13A shows an Epoch that has continuity between two AV clips;

FIG. 13B shows how Display Sets of an Epoch Continue type are managed;

FIG. 14 shows three conditions necessary for continuity between two AVClips;

FIG. 15 shows a screen composition for DSm and a screen structure DSm+1for comparison;

FIG. 16 shows an Epoch divided into two parts at a boundary between AVClips;

FIG. 17 shows how an Epoch Continue is managed at a branch point whentwo AV Clips (AV Clip #2 and AV Clip #3) are available to follow asingle AV Clip (AV Clip #3);

FIG. 18 shows how an Epoch Continue is managed at a point, where twopreceding AV Clips (AV Clip #1 and AV Clip #4) merge to a single AV Clip(AV Clip #2);

FIG. 19 shows files having an extension “clpi” and files having anextension “mpls”;

FIG. 20 shows a structure of a piece of PL information;

FIG. 21 shows an example of pieces of PL information in the case wheretwo AV Clips are to be managed as a single PlayList;

FIG. 22 shows a Display Set belonging to each PlayItem (AV Clip), andthe connection_condition of each PlayItem;

FIG. 23 shows an Epoch that contains DSm+1 at the head of PlayItem #2 (afollowing AV Clip), and DSm at an end of PlayItem #1;

FIG. 24 shows an internal structure of a reproduction device of thepresent invention;

FIG. 25 is a flow chart showing a processing order for loadingfunctional segments;

FIG. 26 shows how Display Sets are read when playing back the two AVclips shown in FIG. 14;

FIG. 27 shows how Display Sets are read to a graphics decoder when skipplayback of the AV Clip #2 is carried out in order;

FIG. 28 shows for comparison a PTS value of a video stream belonging tothe preceding AV Clip and a PTS value of a video stream belonging to thefollowing AV Clip;

FIG. 29A shows a structure of an interactive graphics stream;

FIG. 29B shows PES packets obtained by converting functional segments;

FIG. 30 shows a logical structure made up of functional segments ofvarious types;

FIG. 31 shows correspondences between ICSs and aninteractive_composition;

FIG. 32 shows a data structure of an ICS;

FIG. 33 shows a data structure of page information for a given page(page y) among a plurality of pages in an x-th Display Set;

FIG. 34 shows setting for a page_version_number field in two consecutiveDisplay Sets (DSx+1, DSx);

FIG. 35 shows settings for the page_version_number field in twoconsecutive Display Sets (DSx+1, DSx);

FIG. 36 shows a page composed of page information (y) in Dsx and Pageinformation (y) in DSx+1 for comparison;

FIG. 37 show a processing order followed by a graphics controller 17when there is an Epoch Continue-type Display Set in an IG stream; and

FIG. 38 is a flow chart showing a manufacturing process for producing aBD-ROM described in the first to third embodiments.

BEST MODE FOR CARRYING OUT THE PRESENT INVENTION

The following describes embodiments of the recording medium of thepresent invention. First, applications of the recording medium of thepresent invention are described. FIG. 1 shows an exemplary applicationof the recording medium. The recording medium in FIG. 1 is a BD-ROM 100.The BD-ROM 100 is used to provide movies in a home theater system thatincludes a reproduction device 200, a remote control 300, and television400.

An application of the recording medium of the present invention isdescribed above. The following describes a way of producing therecording medium. The recording medium can be produced by makingimprovements to a BD-ROM application layer.

FIG. 2 shows an application layer format of a BD-ROM expressed using adirectory structure. As shown in FIG. 2, The BD-ROM includes a BDMVdirectory under a ROOT directory.

Subordinate to the ROOT directory there are four subdirectories Theseare a PLAYLIST directory, a CLIPINF directory, a STREAM directory, and aBDJA directory. The STREAM directory stores a file group constitutingdigital streams. Each file has an extension “m2ts”, and the file groupincludes 00001.m2ts, 00002.mts, and 00003.m2ts.

The PLAYLIST directory stores a file group constituting staticscenarios. Each file has an extension “mpls”, and the file groupincludes 00001.mpls, 00002.mpls, and 00003.mpls.

The CLIPINF directory stores a file group constituting static scenarios,similarly to the PLAYLIST directory. Each file has an extension “clpi”,and the file group includes 00001.clpi, 00002.clpi, and 00003.clpi.

In FIG. 2, the files with the extension “m2ts” (00001.m2ts, 00002.mts,00003.m2ts . . . ) store AV Clips. The AV Clips include Main Clips andSubclips. Each Main Clip is a digital stream generated by multiplexing aplurality of elementary streams, typical examples of which include avideo stream, an audio stream, a presentation graphics stream (PGstream) constituting subtitles, and an interactive graphics stream (IGstream) constituting menus.

FIG. 3 shows a typical structure of an AV Clip.

The AV Clip (see middle level in FIG. 3) is constructed as follows. Thevideo stream which is made up of a plurality of video frames (picturespj1, pj2, pj3, . . . ) and the audio stream which is made up of aplurality of audio frames (upper level 1) are each converted to PESpackets (upper level 2), and further converted to TS packets (upperlevel 3). Likewise, the Presentation Graphics stream (PG stream) whichis made up of subtitles and the like and the Interactive Graphics stream(IG Stream) (lower level 1) are converted to PES packets (lower level2), and subsequently converted to TS packets (lower level 3). These TSpackets of the video, audio, Presentation Graphics and InteractiveGraphics streams are multiplexed to generate the AV Clip.

When recorded on a BD-ROM each of the TS packets included in the AV Clipis allocated an extension header. The extension header is calledTP_extra_header, is 4 bytes in length, and includes anarrival_time_stamp and a copy_permission_indicator. The TS packets withattached TP_extra_headers are collected into groups each containing 32packets, and written to 3 sectors of the BD-ROM. Each group containingthe 32 packets is 6144 bytes (=32×192) in size, and therefore matchesthe 6144-byte size (=2048×3) of the three sectors. In combination, thethree sectors storing the 32 TS packets with attached TP_extra_headersare called an “Aligned Unit”.

The AV clip is described above. The following describes the PresentationGraphics stream. FIG. 4A shows a structure of the Presentation Graphicsstream. Level 1 shows the TS packets that make up the AV Clip. Level 2shows the PES packets that make up the graphic stream. Each PES packetin level 2 is formed by extracting the payloads of TS packets with aprescribed PID from the TS packets in level 1, and combining theextracted payloads.

Level 3 shows a structure of the graphics stream. The graphics streamincludes functional segments called a PCS (Presentation CompositionSegment), a WDS (Window Definition Segment), PDS (Palette DefinitionSegment), an ODS (Object Definition Segment), and an END (END of DisplaySet Segment). Of these functional segments, the PCS is a screencomposition segment, and the WDS, PDS, ODS and END are definitionsegments. The PES packets are in one-to-one correspondence with thefunctional segments. Each functional segment is either converted to asingle PES packet and recorded on the BD-ROM or fragmented, converted toa plurality of PES packets and recorded on the BD-ROM.

FIG. 4B shows PES packets obtained by converting functional segments. Asshown in FIG. 4B, the PES packets are composed of “packet headers” and“payload”, where the payload is the functional segment. Besides thepayload, each packet has a corresponding DTS and PTS. Hereinafter, theDTS and PTS in the header of the PES packet that contains the functionalsegment are regarded as the DTS and PTS of that functional segment.

These functional segments of various types make up a logical structureof the type shown in FIG. 5. In FIG. 5, level 3 shows functionalsegments, level 2 shows Display Sets, and level 1 shows Epochs. EachDisplay Set (abbreviated to DS) in level 2 is a string of functionalsegments, from the functional segments that make up the graphics stream,that together make up a single screen of graphics. In FIG. 5, brokenlines kz1 indicate which DS the functional segments belong to. It isclear from the figure that the string of functional segments denoted byPCS-WDS-PDS-ODS-END compose one DS. The reproduction device reads theplurality of functional segments that compose the single DS to produceone screen of graphics.

Each Epoch in level 1 is a time period, on the playback time axis of theAV Clip, over which memory management is continuous, and a group of dataallocated to that time unit. The memory to be managed includes aGraphics Plane for storing one screen of Graphics and an Object Bufferfor storing uncompressed graphics data. Saying that memory management iscontinuous over the Epoch means that (i) neither the Graphics Plane norObject Buffer is flushed during the Epoch (where to flush means to clearthe entire Graphics Plane or the Entire Object Buffer), and (ii)deletion and rendering of graphics are performed only within apredetermined rectangular area of the Graphics Plane during the Epoch.In other words the rectangular area is fixed in size and position overthe Epoch. When deletion and rendering of graphics is confined to thefixed rectangular area, synchronization of graphics and video isguaranteed. In other words, the Epoch is a time unit on the playbacktime axis during which the synchronization of video and graphics isguaranteed. To change the predetermined area for whichrendering/deletion is performed, it is necessary to define a changepoint on the playback time axis and set a new Epoch from that pointforward. In this case, synchronization of video and graphics is notguaranteed at the boundary between the two epochs.

With regard to subtitling, a time period on the reproduction time axisduring which subtitles appear within a fixed rectangular area can be asingle Epoch. FIG. 6 shows the relationship between subtitle displaypositions and Epochs, and may be considered to show a situation in whichsubtitle display positions are changed depending on picture form. Of thefour subtitles, which are “Honestly”, “I'm sorry”, “That happened”“three years ago”, two are positioned at the top of the screen and twoat the bottom. More specifically, “Honestly” and “I'm sorry” are at thebottom and “That happened” and “three years ago” are at the top. Thesubtitle display positions are altered so as to correspond with emptyregions of the screen in order to make the subtitles easier to see. Inthis case, the time period on the AV Clip time playback time axis duringwhich the subtitles are displayed at the bottom of the screen is Epoch1,and the time period during which the subtitles are displayed at the topof the screen is Epoch 2. Thus, each of the two Epochs has a separatesubtitle rendering area. In Epoch 1, the subtitle rendering area (Window1) is in the bottom margin of the screen. In Epoch 2 the subtitlerendering area (Window 2) is in the top margin of the screen. In each ofEpoch 1 and Epoch 2 continuous memory management of the Graphics Planeand buffer is guaranteed, so the subtitles are displayed seamlessly inthe corresponding margin. This completes the description of the Epoch.The following describes a Display Set.

In FIG. 5 broken lines hk1 and hk2 indicate an Epoch, in level 1, thatcontains the Display Sets in level 2. As is clear from FIG. 5, a seriesof DS, including an Epoch Start DS; an Acquisition Point DS, and aNormal Case DS, constitute the Epoch. Note that the Epoch Start DS,Acquisition Point DS, and Normal Case DS denote types of DS. Though theAcquisition Point DS precedes the Normal Case DS in FIG. 5, this ismerely an example and the order may be reversed.

The Epoch Start DS indicates the beginning of a new Epoch. Thus, theEpoch Start DS contains all the functional segments necessary for a nextscreen composition. The Epoch Start DS is provided at a position likelyto be chosen as a starting point, such as the beginning of a section ina movie.

The Acquisition Point DS is not an Epoch starting point, but containsall functional segments necessary for a next screen composition. As aresult, graphics can be displayed reliably if playback is started fromthe Acquisition Point DS. In other words, the Acquisition Point DSenables screen composition from a midpoint in the Epoch.

The Acquisition Point DS is provided at a position that may be chosen asa starting point, such as a position that is specifiable using a timesearch. “Time search” is to an operation by which a user inputs a numberof minutes/seconds to locate a playback point. If the input units are,say, 10 seconds (or 10 minutes), corresponding playback pointspositioned at intervals of 10 seconds (or 10 minutes), will bespecifiable using the time search. If the Acquisition Point DSs areprovided in positions that are specifiable using the time search, thegraphics stream can be played back satisfactorily when the time searchis performed.

The Normal Case DS contains only difference data relative to theprevious Display Set. For example, if a DSv has the same subtitles as animmediately preceding Dsu but has a different screen composition fromthe DSu, the DSv will be a Normal Case DS containing only a PCS and anEND. With this arrangement, there is no need to provide ODSs that havealready been provided. As a result, the amount of data stored on theBD-ROM can be reduced. On the other hand, it is not possible to displaygraphics using only the Normal Case DS containing difference data.

The following describes the Definition Segments (ODS, WDS, and PDS).

The Object_Definition_Segment is a functional segment for defining agraphics Object. The following describes this graphics Object. AV Clipsrecorded on BD-ROMs feature an image quality equivalent to that ofhigh-definition television pictures. The resolution for displayinggraphics Objects is set to an equivalently high 1920×1080. This highresolution permits reproduction of movie theater style subtitles (e.g.crisp handwriting style subtitles) using BD-ROMs. A graphics Object ismade up of plurality of pieces of run-length data. Run-length dataexpresses a Pixel String using a Pixel Code that indicates a pixel valueand a continuous length of the pixel value. The Pixel Code is 8 bits inlength, and takes a value of 1 to 255. The Run-length data is able toselect 256 colors of a possible 16,777,216 in accordance with the PixelCode, and set the pixel color. Note that when a graphics. Object is asubtitle, it is necessary to dispose a character string on a transparentbackground.

The ODS defines a graphics Object according to a data structure shown inFIG. 7A. As shown in FIG. 7A, the ODS is composed of a segment_typefield indicating that the segment is of the ODS type, a segment_lengthfield indicating a data length of the ODS, an object_id field uniquelyidentifying the graphics Object in the Epoch, an object_version_numberfield indicating a version of the ODS in the Epoch, alast_in_sequence_flag filed, and an object_data_fragment fieldcontaining a consecutive sequence of bytes corresponding to part or allof the graphics Object.

The Palette Definition Segment (PDS) is a functional segment for storingpalette data. The palette data indicates combinations of Pixel Codes of1 to 255 and pixel values. Each pixel value is composed of a reddifference component (Cr value), a blue difference component (Cb value),a luminance component (Y value), and a transparency (T value). Eachpixel code in the run length data is exchanged for a pixel valueindicated by the palette to generate a color. The data structure of PDSis shown in FIG. 7B. As shown in FIG. 7B, the PDS includes asegment_type field indicating that the segment is of the PDS type, asegment_length field indicating a data length of the PDS, a palette_idfield for uniquely identifying the palette included in the PDS, apalette_version_number field indicating a version of the PDS within theepoch, and a palette_entry field carrying information for each entry.The palette_entry field indicates a red difference component (Cr_value),a blue difference color component (Cb_value), a luminance component(Y_value), and a transparency (T_value) for each entry.

The following describes the WDS.

The window_definition_segment is a function segment that defines arectangular area on the Graphics Plane. As described above, continuousmemory management over an Epoch is only possible if clearing andrendering are limited to a fixed rectangular area on the Graphics Plane.The rectangular area on the Graphics Plane is called a “Window”, and isdefined by WDS. FIG. 8A shows the data structure of the WDS. As shown inFIG. 8A, the WDS is expressed using a window_id field uniquelyidentifying the Window on the Graphics Plane, awindow_horizontal_position field indicating the horizontal position of atop left pixel on the Graphics Plane, and a window_vertical_positionfield indicating a vertical position of a top left pixel on the GraphicsPlane, a window_width field indicating a width of the Window on theGraphics Plane, and a window_height field indicating a height of theWindow on the Graphics Plane.

The window_horizontal_position field, the window vertical_positionfield, the window_width field, and the window_height field can containthe following values. The Graphics Plane serves as a coordinate systemfor these field values. This Graphics Plane has a two-dimensional sizedefined by video_height and video_width parameters.

The window_horizontal_position field specifies a horizontal position ofthe top left pixel of the Window on the Graphics Plane, and thus takesvalue in a range of 1 to the video_width. The window_vertical_positionfield specifies the vertical position of the top left pixel of theWindow on the Graphics Plane, and thus takes a value in a range of 1 tothe video_height.

The window_width field specifies the width of the Window on the GraphicsPlane, and thus takes a value in a range of 1 to(video_width)−(window_horizontal_position). The window_height fieldspecifies the height of the Window on the Graphics Plane, and thus takesa value in a range of 1 to (video_height)−(window_vertical_position).

A position and size of a Window can be defined for each Epoch using thewindow_horizontal_position, window_vertical_position, window_width, andwindow_height fields in the WDS. The author is therefore able to makeadjustments to a Window at time of authoring to ensure that there is nointerference with elements of the picture over the period of an Epoch.For instance, the Window may be made to appear in a desired margin.Subtitles displayed using graphics can be clearly viewed. Moreover,since it is possible to define a WDS for each epoch, the graphics can bemoved as elements of the picture change with time. This enables a clearview of the graphics to be maintained. As a result, the quality of themovie product can be raised to the level of a cinema film, in whichsubtitles are integrated into the picture.

The following describes an END of Display Set Segment. The END ofDisplay Set Segment is a functional segment indicating that transmissionof a Display Set is complete, and is positioned immediately after thelast ODS in the Display Set. The END of Display Set Segment includes asegment_type field indicating that the segment is of the END of DisplaySet type, and a segment_length field indicating a data length of the ENDof Display Set Segment. The END of Display Set Segment is not a mainfeature of the present invention. Thus, further description of the ENDof Display Set Segment is omitted.

The ODS, PDS, WDS and END are described above. The following describesthe PCS.

The PCS is a functional segment for constituting an interactive screen.FIG. 8B shows a data structure of the PCS. As shown in FIG. 8B, the PCSincludes a segment_type field, a segment_length field, acomposition_number field, a composition_state field, a palette_updatefield, a palette_id_ref field, and composition_object fields (1) to (m).

The composition_number field identifies a graphics update in the DisplaySet, using a number from 0 to 15. Specifically, the composition_numberfield is incremented by one for each graphics update from the beginningof the Epoch to the PCS containing the composition_number field.

The composition_state field indicates whether the Display Set startingfrom the PCS is a Normal Case-type Display Set, an AcquisitionPoint-type Display Set, or an Epoch Start-type Display Set.

The palette_update_flag field indicates whether the PCS describes aPalette-only Display Update. The Palette-only Display Update is anupdate that is limited to replacing the palette with a new palette. Toindicate a Palette-only Display Update, the palette_update_flag is setto 1.

The palette_id indicates whether the PCS describes a Palette-onlyDisplay Update. The Palette-only Display Update is an update that islimited to replacing the palette with a new palette. To indicate aPalette-only Display Update, the palette_update_flag is set to 1.

The composition_object fields (1) to (m) each contain controlinformation for realizing a screen composition using the Display Set towhich the PCS belongs. In FIG. 8 b, a composition_object (i) isexpanded, as indicated by broken lines wd1, to illustrate an internalstructure of the composition_object fields. As illustrated, thecomposition object (i) includes an object_id_ref, a window_id_ref, anobject_cropped_flag, an object_horizontal_position, anobject_vertical_position, and cropping_rectangle_information (1) tocropping_rectangle_information (n).

The object_id_ref field contains a reference value that is an object_idassociated with a graphics Object. This reference value identifies thegraphics Object that is to be used to produce a section of the screencomposition corresponding to the composition_object (i).

The window_id_ref field contains a reference value that is a Windowidentifier (window_id). This reference value specifies the Window inwhich the graphics Object is to be displayed in order to produce thesection of the screen composition corresponding to thecomposition_object (i).

The object_cropped_flag field indicates whether or not a graphics Objectcropped in the Object Buffer is to be displayed. When theobject_cropped_flag field is set to 1, the cropped graphics Object inthe Object Buffer is displayed When the object_cropped_flag field is setto 0, the cropped graphics Object in the Object Buffer is not displayed.

The object_horizontal_position field specifies a horizontal position ofa top left pixel of the graphics Object on the Graphics Plane.

The object_vertical_position field specifies a vertical position of atop left pixel of the graphics Object on the Graphics Plane.

The cropping_rectangle information (1) to cropping rectangle information(n) fields are valid when the object_cropped_flag field is 1. Thecropping_rectangle information (i) is expanded, as indicated by brokenlines wd2, to illustrate an internal structure of thecomposition_rectangle information. As illustrated, thecropping_rectangle information (i) includes anobject_cropping_horizontal position field, an object_cropping_verticalposition field, and object_cropping_width field, and anobject_cropping_height field.

The object_cropping_horizontal position field specifies a horizontalposition of a top left corner pixel of a cropping rectangle in thegraphics Object. The cropping rectangle is used to remove a portion ofthe graphics Object, and corresponds to a “region” in the ESTI EN 300743 standard.

The object_cropping_vertical position field specifies a verticalposition of the top left corner pixel of the cropping rectangle on theGraphics Object.

The object_cropping_width field specifies a width of the croppingrectangle in the Graphics Object.

The object_cropping_height field specifies a height of, the croppingrectangle in the Graphics Object.

The data structure of the PCS is described above. The followingdescribes a specific example of the PCS. In the example, the subtitles“Honestly” and “I'm sorry” shown in FIG. 6 are displayed in sequence bywriting to the graphics plane three times as the moving picture isreproduced. FIG. 9 illustrates how the subtitles are realized. In FIG.9, an Epoch includes DS1 (Epoch Start) and DS2 (Normal Case). The DS1includes a WDS defining a window in which the subtitles are to bedisplayed, an ODS including the line “Honestly, I'm sorry”, and a firstPCS. The DS2 includes a second PCS.

The following describes each PCS. FIGS. 10 to 12 show examples of theWDS and PCS. FIG. 10 shows the PCS in DS1.

In FIG. 10, a window_horizontal_position field value and awindow_vertical field value in the WDS specify top left coordinates LP1of the Window on the Graphics Plane, and a window_width field value anda window_height field value in the WDS specify a height and width of theWindow.

In FIG. 10, an object_cropping_horizontal_position field value and awindow_vertical_position field value specify a basepoint ST1 of acropping rectangle in a coordinate system whose origin is the top leftof the of the Graphics Object in the Object Buffer. The croppingrectangle (enclosed by a thick line) is then defined using anobject_cropping_height field value, an object_cropping_width field valueand the basepoint ST1. The cropped graphics Object is then disposed in aregion cp1 (enclosed by a broken line) so that a top left corner of thecropped Graphics Object lies at a pixel specified by anobject_horizontal_position field value and an object_vertical positionfield value in the coordinate system of the Graphics Plane. This causes“Honestly” to be written into the window of the graphics plane.Consequently, the subtitle “Honestly” is displayed in combination withthe moving picture.

FIG. 11 shows the PCS in DS2. Since the WDS inn FIG. 11 is the same asthat of FIG. 10 its description is omitted. The cropping rectangle inFIG. 11, however, differs from that of FIG. 10. Anobject_cropping_horizontal_position and anobject_cropping_vertical_position specify top left coordinates of acropping rectangle corresponding to “I'm sorry” from the line “HonestlyI'm sorry”, and the object_cropping_height and object_cropping_widthspecify a height and width of the cropping rectangle corresponding to“I'm sorry”. This causes “I'm sorry” to be written into the Window onthe Graphics Plane. Consequently, the subtitle “I'm sorry” is displayedin combination with the moving picture.

The functional segments are described above. The following describes themanner in which Display Sets including PCSs and ODSs are allocated tothe playback time axis of the AV Clip. An Epoch is a period on theplayback time axis over which memory management is continuous, and eachEpoch constitutes, one or more Display Sets. At issue, therefore, is themanner in which the one or more Display Sets are allocated to theplayback time axis. Note that the playback time axis is an assumed axisused to prescribe decoded timings and playback timings for each frame ofpicture data making up the video stream that is multiplexed into the AVClip. The decode timing and playback timing are expressed to an accuracyof 1/90000 seconds. The DTS and PTS associated with the PCS and ODS inthe Display Set specify timings for synchronous control on the playbacktime axis. In other words, the DSs are allocated to the playback timeaxis by carrying out synchronous control using the DTSs and PTSsassociated with the PCSs and ODSs.

A Display Set DSn of the Display Sets belonging to the Epoch isallocated to the playback time axis using a PTS and DTS which are set asshown in FIG. 12. FIG. 12 shows the AV Clip playback time axis to whichthe DSn has been allocated. In FIG. 12, the start of the DSn period isspecified by a DTS value (DTS(DSn[PCS]) of a PCS belonging to the DSn,and the end of the period is specified by a PTS value (PTS(DSn[PCS])) ofthe same PCS. The timing for the first display is also specified by thePTS value (PTS(DSn[PCS]) if the PCS. If the timing of a desired picturein a video stream is matched with the PTS(DSn[PCS]), first display ofthe DSn will synchronize with the video stream.

The PTS(DSn[PCS]) is a value obtained by adding DTS(DSn{PCS}) a periodfor decoding ODS (DECODEDURATION) to the DTS(DSn[PCS]).

Decoding necessary for the first display of the DSn is performed in theDECODEDURATION. In FIG. 12, a period mcl is a period during which anarbitrary ODS(ODSm) belonging to the DSn is decoded. The starting pointof the decode period mcl is specified by DTS(ODSn[ODSm]), and the endpoint of the decode period mcl is specified by PTS(ODSn[ODSm]).

The Epoch is therefore prescribed by allocating each of the ODSs in theEpoch to the playback time axis. The above describes the allocation tothe playback time axis.

The Epoch is a unit over which memory management in the graphics decoderis continuous. Thus, it is normally necessary that the Epochs finishwithin a single AV Clip. However, when two AV Clips are played back insequence and three prescribed conditions are met, it is possible todefine an Epoch that is continuous over the boundary between the AVClips.

FIG. 13A shows an Epoch that is continuous across a boundary between twoAV Clips. Level 1 in FIG. 13A shows the two AV Clips that are to beplayed back consecutively. Level 2 shows an Epoch that is continuousacross a boundary between the two AV Clips. Level 3 shows the DisplaySets that belongs to the Epoch in level 2. The Epoch shown in level 2 isnot divided at the boundary between AV Clips. In the Display Sets inlevel 3, however, there is a boundary between the Display Sets at theboundary between the AV Clips. Note that in FIG. 13A the Display Set(DSm+1) positioned immediately after the boundary between the AV Clipsis of an Epoch Continue type.

Epoch Continue refers to the type of the Display Set (DSm+1) positionedimmediately after the boundary between the AV Clips. The Display Set(DSm+1) is treated as an Acquisition Point if the three prescribedconditions are met, and an Epoch Start if one or more of the threeconditions is not met.

FIG. 13B shows the manner in which display a Display Set of the EpochContinue type is treated. As is clear from FIG. 13B, the Display Set ofthe Epoch Continue type is treated as an Epoch Start in the case of skipplayback from a subsequent AV clip, and as an Acquisition Point in thecase of consecutive playback from the immediately preceding AV Clip.

FIG. 14 shows the conditions for ensuring continuity between the two AVClips. Level 1 in FIG. 14 shows two AV Clips that are to be played backconsecutively and level 2 shows three Epochs. Of these three Epochs, themiddle Epoch is the one in which memory management is continuous acrossthe boundary between the two AV Clips. Level 3 shows Display Sets thatbelong to respective Epochs. The Epochs in level 2 have boundaries thatdiffer in position from the boundaries of the AV Clips. Level 4 showsthe functional segments that belong to each Display Set. The group offunctional segments in level 4 is the same as that in level 4 of FIG. 5.The symbols double circle 1, double circle 2, and double circle 3 inFIG. 14 indicate the conditions for establishing an Epoch withcontinuity across the boundary between the two AV Clips. The firstcondition is that the Display Set (DSm+1) positioned immediately afteran AV Clip Boundary is of the Epoch Continue type.

The second condition is that a composition number in a PCS belonging tothe DSm+1 is identical to a composition_number (=A) in a PCS belongingto the DSm, which immediately precedes the DSm+1 (i.e. the content ofthe graphics is the same before and after the boundary between the twoAV clips). The composition_number refers to a screen composition thatuses the Display Set. Thus, if the composition_numbers in the DSm andDSm+1 are equal, the graphics obtained using screen compositionscorresponding to these Display Sets are the same. FIG. 15 shows thescreen composition of DSm and the screen composition of DSm+1 forcomparison. As shown in FIG. 15, the graphics corresponding to the DSmare “three years ago”, and the graphics corresponding to the DSm+1 arealso “three years ago”. Thus, the graphics produced by the two displaysets are identical, and it is clear that the Composition_numbers will beidentical. Also, since the video streams are played back seamlessly, theDSm+1, it is clear that the DSm+1 will be treated as an acquisitionpoint.

The third condition is that playback of the AV Clip and the immediatelyfollowing AV Clip is seamless. Seamless playback of the video stream isconditional upon the following.

(i) The display method (e.g. NTSC, PAL) for the video stream, which isspecified by attribute information, is the same in both AV Clips.

(ii) The encoding method (e.g. NTSC and PAL) for the audio stream, whichis specified by the attribute information, is the same in both AV Clips.

If, in (i) and (ii), the display methods and encoding methods for thevideo and audio streams are different, seamless playback cannot beperformed because the video decoder and audio decoder stop operatingmomentarily in order to switch to a new display format, encoding modeand bit rate.

For example, when two audio streams are to be played back consecutivelyand one is encoded using the AC-3 method and the other using an MPEGstandard, the audio decoder stops decoding momentarily between the twostreams in order to carry out an internal switch of attributes. The casewhen the video streams are different is similar.

Seamless playback, therefore, only takes place when the conditions of(i) and (ii) are satisfied. If any of the above conditions is notsatisfied, seamless playback is not permitted.

If the three conditions are met, the DSm+1, which is of the EpochContinue type, is treated as an Acquisition Point. In other words, theDisplay Sets 1 to m and the Display Sets m+1 to n form a single Epoch,and the state of the buffer in the Graphics decoder is maintained whentwo AV clips are played back consecutively.

Note that, even if the DSm+1 is of the Epoch Continue type, in the casethat one or both of the remaining conditions are unsatisfied, the Epochwill be divided at the boundary between the AV Clips. From the above itis clear that the Display Set of the Epoch Continue type is only treatedas an Acquisition Point if the three conditions are satisfied. If anyone or more of the conditions is not satisfied, the Display Set of theEpoch Continue type is treated as an Epoch Start. FIG. 17 shows themanner in which an Epoch Continue type Display Set is managed when thereare two preceding, AV Clips (AV Clip#2 and AV Clip#3) for a given AVClip (AV Clip#1). Of the two types of preceding AV Clip, AV Clip#1 is ofthe type shown in FIG. 14. The AV Clip#2 that is to follow the AV Clip#1is also of the type shown in FIG. 14. The AV Clip#1 and the AV Clip #2therefore satisfy all three of the conditions. Thus, when played backafter AV Clip#1, the first DS (DSm+1) in AV Clip#2 is treated as anEpoch Continue. The other following AV Clip, which is the AV Clip#3, hasexactly the same graphic content as the AV Clip#2. Also, thecomposition_number in the last DS (DSn) of AV Clip#1 matches thecomposition_number in the first AV Clip#3. Therefore, when AV Clip#3follows AV Clip#1, all three conditions are satisfied, and the EpochContinue type Display Set is treated as an Acquisition point.

FIG. 18 shows how an Epoch Continue is managed at a merge point when twopreceding AV Clips (AV Clip #1 and AV Clip #4) merge to a single AV Clip(AV Clip#2). Both AV Clip#1 and AV Clip#2 are of the type shown in FIG.14, and satisfy the three conditions. Thus, in the case that AV Clip#1is played back first, the first DS (DS1) in AV Clip2 will be treated asan Epoch Continue. The AV Clip#4 has exactly the same graphic content asthe AV Clip#1. Also, the composition_number in the in the last DS (DSm)of AV Clip#4 matches the composition_number in the first DS (DS1) of theAV Clip#2. Thus, in the case that the order of playback is AV Clip#4 toAV Clip#2, the three conditions are satisfied, and the Epoch Continuetype Display Set is treated as an Acquisition Point.

The above describes the AV Clip. The following describes files havingthe file extensions “clpi” and “mpls”. FIG. 19 shows files having theextension “clpi” and files having the extension “mpls”.

The files having the file extensions (0001.cpli, 0002.cpli, 0003.cpli .. . ) are pieces of management information in one to one correspondencewith the AV clips. The pieces of management information includeinformation such as coding format of the AV Clips in the stream, a framerate, a bit rate, and a resolution. Each piece of management informationalso has an EP Map and an ATC_Delta for indicating the head position ofa GOP. The ATC (Arrival Time Clock) in ATC_Delta refers to a clocksignal used a reference for the ATS. The ATC_Delta indicates thedifference between the ATC of the preceding AV Clip and the ATC of thefollowing ATC Clip.

The files having the extension “mpls” (0001.mpls, 0002.mpls, 0003.mpls .. . ) store pieces of PL information. Each piece of PL informationdefines a playlist by reference to the AV Clips. FIG. 20 shows acomposition of PL information. As shown on the left side of FIG. 19,marked by mp1, each piece of PL information is composed of a pluralityof pieces of PlayItem information each denoted as (PlayItem( )). ThePlayItem is a playback section defined by specifying an in_time and anout_time on one or more AV Clip time axes. A PlayList (PL) composed of aplurality of playback sections is then defined by providing a pluralityof pieces of Play Item information. The broken lines marked mp2 in FIG.20 point indicate a close up of a composition of one piece of PlayIteminformation. As shown in FIG. 20, each piece of PlayItem information iscomposed of a clip_information_file_name field, an in_time field, anout_time field, and a connection_condition field.

Settings in a piece of PL information when two AV Clips are treated as asingle PlayList are described, with reference to FIG. 21. Level 1 inFIG. 21 shows the two AV Clips of FIG. 15. Level 2 in FIG. 21 shows thePlayList playback time axis defined by the corresponding piece of PLinformation. The piece of PL information includes two pieces of PlayIteminformation (PlayItem#1 and PlayItem#2). The preceding AV Clip andfollowing AV Clip are treated as a single PlayList if the in_time fieldand the out_time field of PlayItem#1 indicate the start point and theend point of the preceding AV Clip and the in_time field and theout_time field of PlayItem#2 indicate the start point and the end pointof the following AV Clip. Level 2 in FIG. 21 shows a playback time axis(PL Playback Time Axis) of the Playlist defined by the piece of PLinformation. When the PlayList is defined in this way, the AV Clip istreated, in a sense, as a section of the PlayList. Each section of thePlayList is called a PlayItem. In other words, the relationshipPlayItem=AV Clips holds true.

In the piece of PlayItem information that defines a PlayItem, there is aconnection_condition field, which indicates whether or not whetherplayback of the corresponding PlayItem is to seamlessly follow playbackof the preceding PlayItem (AV Clip).

FIG. 22 shows Display Sets belonging to each PlayItem (AV Clip), and theconnection_condition field of each PlayItem. In FIG. 22, if the DisplaySet (DSm+1) at the head of PlayItem#2 is of the Epoch Continue type, andthe connection_condition field in the PlayItem#2 indicates a seamlessconnection, the DSm+1 at the head of the PlayItem#2 (the following AVClip) and the DSm at the end of the PlayItem#1 (the preceding AV Clip)belong to a same Epoch. FIG. 23 shows the Epoch containing the DSm+1 atthe head of the PlayItem#2 (the following AV Clip) and the DSm at theend of the PlayItem#1 (the preceding AV Clip). Since the last DisplaySet in the preceding AV Clip and the first Display Set of the followingAV Clip belong to the same Epoch, the graphics display resulting fromthese two Display Sets will be continuous.

The above-described data structures of the Display Sets (PCS, WDS, PDS,and ODS) are instances of class structures described in programminglanguage. A producer authoring a BD-ROM is able to obtain such datastructures on the BD-ROM by describing a desired class structure usingsyntax stipulated by a Blu-ray Disc Read Only Format. The abovedescribes the recording medium of the embodiments of the presentinvention. The following describes the reproduction device of theembodiments of the present invention. FIG. 24 shows an internalstructure of the reproduction device of the present invention. Thereproduction device of the present invention is commercially producedwith an internal structure based on that shown in FIG. 24. Thereproduction device of the present invention is mainly composed of threeparts, these being system LSI, a drive device, and a microcomputersystem, and can be commercially produced by equipping a base and cabinetwith these parts. The system LSI is an integrated circuit includingvarious processing units each with a reproduction device-relatedfunction. Reproduction devices produced in this way are constructed froma BD drive 1, and arrival time clock counter 2 a, a source de-packetizer2 b, a PID filter 3, Transport Buffers 4 a, 4 b and 4 c, surroundingcircuitry 4 d, a video decoder 5, a video plane 6, an audio decoder 7, agraphics plane 8, a CLUT unit 9, an adder 10, a graphics decoder 12, acoded data Buffer 13, a surrounding circuitry 13 a, a stream graphicsprocessor 14, an object buffer 15, a composition buffer 16, and agraphics controller 17.

The BD-ROM drive 1 loads/ejects BD-ROMs, accesses a loaded BD-ROM, andfrom the loaded BD-ROM, reads an aligned unit composed of 32 sectors.

The arrival time clock counter 2 a generates an arrival time clock basedon a 27 MHz liquid crystal oscillator. An Arrival Time Clock is a clocksignal providing a time axis used as a reference for the ATS attached tothe TS packets.

When the Aligned Unit composed of the 32 sectors is read from theBD-ROM, the source de-packetizer 2 b extracts a Tp_extra_header fromeach of the TS packets that constitute the Aligned Unit, and outputs thestripped TS packets to the PID filter 3. Output of each stripped TSpacket to the PID filter 3 takes place when the time measured by thearrival time clock counter 2 a reaches the ATS indicated by thecorresponding TP_extra_header. Since the output to the PID filter 3 ismade at the timing indicated by the ATS, the TS packets are output tothe PID filter 3 in accordance with the time measured by the arrivaltime clock, even in the case where the speed of reading from the BD-ROMvaries between, for instance, a 1× speed and a 2× speed.

When two AV Clips are to be played back so that one immediately followsthe other, the source depacketizer 2 b and corrects variation betweenthe ATC of each of the AV Clips using the ATC_Delta present in the Clipinformation.

The PID filter 3 judges whether a TS packet belongs to the video stream,the PG stream, or the IG stream by referring to the attached PID, andoutputs to one of the transport buffers 4 a, 4 b or 4 c accordingly.

The transport buffers 4 a, 4 b and 4 c are memories which store the TSpackets outputted from the PID filter 3 on a first-in first-out basis.

The surrounding circuitry 4 d contains wire logic circuitry forperforming processing to convert TS packets read from the transportbuffers 4 a, 4 b and 4 c into functional segments. The functionalsegments obtained from the conversion are stored in the coded databuffer 13.

The video decoder 5 decodes the plurality of TS packets outputted fromthe PID filter 3 to obtain a picture in an uncompressed format andwrites the picture to the video plane 6.

The video plane is a plane memory used when presenting moving picturedata.

The audio decoder 7 decodes the TS packets outputted from the PIDfilter, and outputs the audio data in an uncompressed format.

The graphics plane 8 is a plane memory having an area large enough forone screen, and is capable of storing the uncompressed graphics data forthe one screen.

The CLUT unit 9 converts index colors in the uncompressed data stored inthe graphics plane 8 based on values of Y, Cr, and Cb indicated by thePDS.

The adding device 10 obtains an overlaid picture by multiplyinguncompressed graphics converted by the CLUT unit 9 by a T value (degreeof transparency), and adding the result, pixel by pixel, to theuncompressed picture data stored in the video plane 6.

The graphics decoder 12 decodes the graphics stream, obtains theuncompressed graphics, and writes the result to the graphics plane 8 asan uncompressed graphics object. Subtitles and menus appear as a resultof decoding the graphics stream.

The graphics decoder 12 is constructed from the coded data buffer 13,the surrounding circuitry 13 a, the stream graphics processor 14, theobject buffer 15, the composition buffer 16, and the graphics controller17.

The coded data buffer 13 is a buffer in which the functional segmentsare stored together with the DTSs and PTSs. The functional segments areobtained by removing the TS packet headers and PES packet headers fromeach TS packet in the transport streams stored in the Transport buffers4 a, 4 b and 4 c, and sequentially arranging the resulting payloads. ThePTSs/DTSs from the removed TS packet headers and PES packet headers arestored in correspondence with the PES packets.

The surrounding circuitry 13 a is wire logic for transmitting data backand forth between the coded data buffer 13 and the graphic streamprocessor 14, and between the coded data buffer 13 and the compositionbuffer 16. In the processing to realize the transmission, if the currentplayback time reaches a time indicated in the DTS of the ODS, thesurrounding circuitry 13 a transmits the ODS from the coded data buffer13 to the stream graphics processor 14. Also, if the current playbacktime reaches a time indicated in the DTS of the PDS or PCS, thesurrounding circuitry 13 a transmits the PCS or PDS to the compositionbuffer 16.

The stream graphics processor 14 decodes the ODS and writes theuncompressed graphics, which are composed of the indexed colors obtainedby decoding, to the object buffer 15 as a graphics object. The streamgraphics processor 14 performs the decoding instantaneously, andtemporarily stores the resulting graphics object. Although the decodingby the stream graphics processor 14 is instantaneous, the writing fromthe stream graphics processor to the object buffer is not completedinstantaneously. In a player that complies with the BD-ROM standard, thestream graphics processor 14 writes to the object buffer 15 at atransmission rate of 128 Mbps. Since the PTS in the END segmentindicates when the writing to the object buffer 15 finishes, the streamgraphics processor waits until the timing indicated by the PTS in theEND segment before processing a subsequent DS. The graphics processor 14starts writing the graphics object obtained by decoding an ODS 15 at atime point indicated by the DTS associated with the ODS and completeswriting by the decode completion time indicated in the PTS associatedwith the ODS.

The object buffer 15 is a buffer for holding the graphics object decodedby the graphics stream processor. The object buffer 15 must be twice orfour times as large as the graphics plane 8. This is to allow scrollingwhich requires the graphics plane to store a graphics object twice orfour times as large as the graphics plane 8.

The composition buffer 16 is memory for holding the PCS and PDS. In thecase that there are two Display Sets to be processed, and an activeperiod of the respective PCSs overlaps, the composition buffer 16 astores a plurality of PCSs.

The graphics controller 17 interprets the PCS. Then, in accordance withthe result of this interpretation, the graphical controller 17 writesthe graphics object to the object buffer 15, reads the graphics objectfrom the object buffer 15 and executes display of the graphics Object.This takes place at the timing indicated by the PTS for PES packetsstored in the PCSs. The interval between display, by the graphicscontroller 17, of a graphics Object belonging to DSn and of a graphicsObject belonging to DSn+1 is the interval described above.

FIG. 25 is a flow chart showing a processing order for loadingfunctional segments. In the flow chart SegmentK is a variable thatrefers to each of the Segments (ICS, PDS and ODS) as they are readduring playback of the AV Clip. A disregard flag indicates whether toload or disregard a given SegmentK. The flow chart is structured toinclude an initialization of the disregard flag to 0 (Step 1), and aloop structure for applying the processing of Steps S2 to S13 to each ofthe Segments (Steps S14 and S15).

The processing of the loop structure (Steps S2 to S15) is repeated foras long as reading of functional segments continues and includes thefollowing. First, it is judged whether the disregard flag is 0 or 1(Step S3). If the disregard flag is 0, the target functional segment istransmitted from the coded data buffer 13 to either the compositionbuffer 16 or to the stream graphics processor 14 (Step S4). If thedisregard flag is 1, no transmission takes place. Instead, the targetfunctional segment is deleted from the coded data buffer 13 (Step S5).

Whether the SegmentK is loaded or disregarded is decided on the basis ofthe disregard flag setting. Steps S9 and S10 are processing steps forsetting the disregard flag.

Step S6 is for judging whether or not composition_state in a PCSindicates Epoch Continue. If SegmentK is of the Epoch Continue type,Steps S7 to S9 are executed. If SegmentK is of the Normal Case type,Steps S10 to S12 are executed.

Note that in Steps S7 to S9 judgments are made in both Step S7 and StepS8, and the disregard flag is set to 1 (Step S9) only if both of thesejudgments are in the affirmative.

Step 7 is for judging whether the connection_condition field of thePlayItem to which the PCS belongs is set to 5 (indicating seamlessconnection). Step 8 is for judging whether the composition_number in anewly read PCS is the same as the composition_number held in thecomposition buffer 16.

If the either of the judgments in Steps S7 and S8 is in the negative,the processing moves to Step 10, and the disregard flag is set to 0. Ifthe judgments in Steps S7 and S8 are both in the affirmative thedisregard flag is set to 1 (Step S9)

Step S11 is a judgment as to whether the composition_state of the newlyread PCS is of the Normal Case type or of the Epoch Continue type. Ifthe composition_state is of the Epoch Start type the disregard flag isset to 0 (Step 10).

Step S11 is a judgment as to whether the composition_state of the newlyread PCS is of the Normal Case type or of the Epoch Continue type. Ifthe composition_state is of the Normal Case type Step S12 is executed asan additional check. Step 12 is for judging whether a graphics Object ispresent in the object buffer, and whether a PCS, PDS and WDS are presentin the composition buffer 16. If all of these are present, the disregardflag is set to 0 (Step 10). If any are lacking, the processing transfersto Step S9.

If there is no graphics object present in the object buffer, it may bethat sufficient functional segments to form an interactive screen werenot originally obtained.

FIG. 26 shows a manner in which Display Sets are read when the two AVclips shown in FIG. 14 are played back. Level 3 shows Display Setsmultiplexed in an AV Clip, level 2 shows a plurality of pictures thatcompose a video stream, and level 3 shows states of the graphicsdecoder.

When DS1, which is positioned at the head of an Epoch, is read, thegraphics decoder is reset, and the coded data buffer 13 reads in orderthe PCS, WDS, PDS, and ODS that compose the DS1. The PCS, WDS and PDSare then transmitted to the composition buffer 16, and the ODS isoutputted to the stream graphics processor.

The arrow mr1 indicates a time at which DSm is read. The coded databuffer 13 reads in order the PCS, WDS, PDS, and ODS constituting theDSm. Since the connection_condition of the DSm is of the AcquisitionPoint type, the PCS, WDS and PDS are discarded without being transmittedto the composition buffer 16. Moreover, the ODS is discarded withoutbeing transmitted to the Stream Graphics Processor.

The arrow mr2 indicates a time at which DSm+1 is read. Here, thegraphics decoder judges whether or not the three conditions have beenmet. If a change stream of the DSm+1 indicates Epoch Continue, ifplayback of the video streams is seamless, and if a composition_numberof DSm+1 matches the composition_number of the PCS in the CompositionBuffer, the three conditions are met, and the DSm+1 is treated as anAcquisition Point. With this method, the reproduction device does notreset the graphics decoder, and discards the PCS, WDS and PDS read fromthe coded data buffer 13 without transmitting them to the compositionbuffer 16. The reproduction devices similarly discards the ODS withoutoutputting it to the Stream Graphics Processor.

The above describes the processing involved in normal playback. In thecase of skip playback of an AV Clip, which occurs as a result ofskipping between chapters, a chapter search, or the like, the playbackdevice instantaneously resets the graphics decoder upon receipt of theskip instruction. Consequently, a current composition_number that ismanaged in the Graphics Decoder, will never match the composition_numberof DSm+1 in the AV Clip about to be played. Consequently, in the case ofskip playback, the DSm+1 is dealt with as an Epoch Start.

FIG. 27 shows a method for reading to a graphics decoder when skipplayback of the AV Clip #2 is carried out in order. Levels 1 to 3 areidentical to those in FIG. 26, and the arrows have the same meaning asin FIG. 26. However, since the content of the graphic display in FIG. 27differs from that of FIG. 26, the composition_number is different. Whenplayback of the following AV Clip begins and the DSm+1 is read by theCoded Data Buffer 13, the graphics decoder interprets the PCS read bythe Coded Data Buffer 13, and makes a judgment about the Change Stream.If the Change Stream is of the Epoch Continue type, the graphics decodermakes judgments about the remaining two conditions. Even if the playbackof the video streams is to be seamless, the graphics decoder treats theDSm+1 as an Epoch Start type Display Set as a result of thecomposition_number being different from the preceding AV Clip.Consequently, the graphics decoder is reset, and the PCS, WDS and PDSread by the coded data buffer 13 is transmitted to the compositionbuffer 16, and the ODS is outputted to the stream graphics processor.

Second Embodiment

The second embodiment relates to setting a PTS for realizing an EpochContinue. When playing two AV Clips in order, it is necessary to takeinto account differences in the clocks used for reference by therespective AV Clips. At authoring, the AV Clips are encoded by differentmachines, and consequently generated based on differing clock signals.The clock used for reference at encoding is known as an STC (System TimeClock). The STC is also used as a reference for the decode processingwhen the reproduction device plays back an AV Clip.

To playback two AV Clips with differing STCs consecutively, the playbackdevice calculates a and STC difference value (STC_delta), adds theSTC_delta to an internal clock time so as to compensate for thedifferences in STCs. FIG. 28 for comparison shows a PTS value of a videostream belonging to the preceding AV Clip and a PTS value of a videostream belonging to the following AV Clip. In the case that A start timefor last graphics display by the playback device during the preceding AVClip is PTS(1stEND), the picture display period is Tpp, and a startingtime at which the first picture of the following AV Clip is displayed isPTS(2ndSTART), the STC_Delta is expressed asSTC_delta=PTS(1stEND)+TP−PTS(2ndSTART).

STC_delta can be expressed in this way because when two AV clips areplayed back consecutively, the PTS(1stEND)+Tpp should matchPTS(2ndSTART), and the difference between the PTS(1stEND)+Tpp andPTS(2ndSTART) can therefore considered to be the difference in the STCs.

When the two AV Clips are to be played back contiguously, both thePTS(1stEND) and the PTS(2ndSTART) are detected and used to calculateSTC_delta. The STC_delta is then added to the counter value of the clockinside the playback device, and the corrected counter value outputted tothe video decoder 5, the audio decoder 7, and the graphics decoder 12.By making reference to the corrected counter value, the video decoder 5,the audio decoder 7, and the graphics decoder 12 are able to play backthe video streams, the audio streams, and the presentation graphicsstreams of the respective AV clips without a pause between the twostreams.

The value of a PTS(DSm+1 [PCS]) of DSm+1 at the head of the graphicsstream belonging to the following AV Clip is adjusted to ensure that theabove-described processing proceeds smoothly. The nature of theadjustment is to have the PTS1(END)+Tpp and PTS(2ndSTART) indicate thesame time. This adjustment is necessary for the following reasons. Ifthe time lag before the first display in the following AV Clip is long,the graphics decoder may be reset. Since the AV Clips in the BD-ROM areeach stored in separate files there is a time lag when reading twoconsecutive files. Consequently, if the reading of the AV Clips is forsome reason further delayed, the risk of reset increases greatly. Todeal with this problem, the Display Set of the Epoch Continue type atthe head of the following AV Clip has the value of PTS (DSm+1 [PCS]) setto indicate an identical time to PTS(1stEND)+Tpp, so that display of thegraphics takes place at a timing identical to display of the firstpicture of the video stream.

Setting the value of PTS(DSm+1) in this way enables the time periodbetween the last display of graphics in the preceding AV Clip and thefirst display in the following AV Clip to be to be minimized, even whenthere is a substantial time lag between completing the reading of thepreceding AV Clip and starting the reading of the following AV Clip.Since the reproduction device is thereby prevented from resetting, thepresence of management data already in the memory can be continuous.

Third Embodiment

The first embodiment describes the PG stream. The third embodiment, onthe other hand, describes the IG stream. The following describes theInteractive Graphics Stream. FIG. 29A shows a structure of anInteractive Graphics Stream. Level 1 shows TS packets that constitutethe AV Clip. Level 2 shows the shows PES packets that constitute thegraphics stream. The PES packets in the level 2 are constructed byextracting payloads from packets having a predetermined PID andconnecting the extracted payloads. Since the presentation graphicsstream is unrelated to the main point of the third embodiment, thepresentation graphics stream is not described below.

The third level shows the construction of the Interactive GraphicsStream. The Interactive Graphics Stream composed of functional segmentscalled ICSs (Interactive Composition Segments), PDSs (Palette DefinitionSegments), ODSs (Object Definition Segments), and ENDS (END of DisplaySet Segments). Of these functional segments, the ICS is known as ascreen composition segment, and the PDS, ODS and END are known asdefinition segments. The PES packets may be in one-to-onecorrespondence, or one-to-many correspondence with the functionalsegments. In other words, each, functional segment is either convertedto a single PES packet and recorded on a BD-ROM or fragmented, convertedinto a plurality of packets and stored on a BD-ROM. FIG. 29B shows thePES packets obtained by converting the functional segments.

The following describes the various functional segments. InteractiveComposition Segments (ICS) are functional segments for controlling thescreen composition of an Interactive Graphics Object. The ICS of thethird embodiment is for realizing a multi-page menu.

The functional segments of various types have a logical structure suchas the one shown in FIG. 30. FIG. 30 shows a logical structure made upof functional segments of various types. Level 1 in FIG. 30 shows anEpoch, level 2 shows a Display Sets, and level 3 shows a each of thevarious types of Display Set. The functional segments shown in level 3of FIG. 29A are shown in level 4 of FIG. 30. The IG stream also containsEpoch Start-type, Acquisition Point-type and Epoch Continue-typefunctional segments. However, the ICS differ from the PCSs in that theAcquisition Point-type functional segments allow for update on apage-by-page basis.

The IG stream is characterized by control of behavior of the multi-pagemenu in accordance with progress, along the above-described playbacktime axis, of moving picture playback. The new composition that allowsthis characteristic to be realized relates to an interactive_compositionin the ICS. The following describes the internal structure of theinteractive_composition.

FIG. 31A and FIG. 31B show the correspondence between the ICS and theinteractive_composition. The relationship between the ICS and theinteractive_composition is either a one-to-one correspondence of thetype shown in FIG. 7A or a one-to-many correspondence of the type shownin FIG. 31B.

The relationship is a one-to-one correspondence when a data size of theinteractive_composition is small enough to be stored in a single ICS.

The relationship is a one-to-many correspondence when a data size of theinteractive_composition is large, and the interactive_composition isfragmented and stored by a plurality of ICS. Since theinteractive_composition can be stored using a plurality of ICS, there isno limit to its data size, which may be increased to, say, 512 kMB, 1MB, or more. A one-to-many correspondence is also possible between theICS and the interactive_composition. However, for simplicity, the casewhere the ICS and the interactive_composition are in one-to-onecorrespondence is used in the following description.

FIG. 32 shows a data structure of an ICS. Each ICS stores either anentire interactive_composition or a portion of aninteractive_composition obtained by fragmentation. As shown in the lefthand side of FIG. 8, the ICS includes a segment_descriptor to indicatethat it is an ICS, horizontal and vertical pixel numbers to be used bythe ICS, a video_descriptor indicating a frame rate, acomposition_descriptor, and an interactive_composition or a portion ofan interactive_composition_data_fragment obtained by fragmentation.

The arrow cu1 in FIG. 32 points to a close-up of a data structure of thecomposition_descriptor As indicated, the composition_descriptor includesa composition_state field that indicates whether a Display Set to whichthe ICS belongs is of the Normal Case-type, the Acquisition Point-type,the Epoch Start-type, or Effect_Sequence-type, and a composition_numberindicating a count of screen combinations.

The arrow cut of FIG. 32 points to a close-up of a data structure of theinteractive_composition. As indicated, the interactive_compositionincludes an interactive_composition_length field, a stream_model field,a user_interface_model field, a composition_time_out_pts, auser_time_out_duration, and pieces of page information (1) (2) . . . (i). . . (number_of_page-1), each of which corresponds to a displayablepage in the multi-page menu.

The interactive_composition_length field indicates the data length ofthe interactive_composition.

The stream_model field indicates a type of stream model theinteractive_composition is using. The stream model indicates the formatused to record the interactive_composition on the BD-ROM, and the mannerin which the interactive_composition is to be managed by the compositionbuffer in the reproduction device. Specifically, the stream modelindicates whether the graphics stream i) has been de-multiplexed from anAV Clip and loaded in the composition buffer or ii) has been preloadedin the composition buffer as a SubClip.

The user_interface_model field indicates whether the user type of userinterface assumed by the interactive_composition is an Always-onU/I or aPop-upU/I. With an Always-onU/I a menu display/deletion occurs inaccordance with playback progress of the AV Clip. With a Pop-upU/I, amenu display/deletion is triggered by a user operation.

The compostion_time_out_pts indicates an end period (Epoch END) of theEpoch to which the ICS belongs. Since interactive control by means ofthe ICS becomes impossible at the end period, the time point indicatedby the composition_time_out_pts indicates the end of interactivecontrol.

The selection_time_out_pts indicates a time period allowed for a buttonin a selected state to automatically activate. More specifically, eachbutton corresponds to an item selection on the multi-page menu, and theselection_time_out_pts stipulates the time taken to alter the button toan active state upon selection.

The IF statement in FIG. 32 (if (Stream_model==‘0b’)) shows that theabove-described composition_time_out_pts and selection_time_out_pts areinformation elements that appear only when the stream_modelfield=multiplexed. If the stream model is preloaded, neither thecomposition_time_out field nor the selection_time_out field are used

The user_time_out_duration field indicates a period of time allowedbefore deletion for a page displayed in response to a user operation. Inthe case of the Always-onU/I, since only pages from the second pageonwards are displayed in response to user operations, only theseSubPages are deleted when the user_time_out duration has elapsed. Afterthe SubPages are deleted, the first page is displayed. In the case ofthe Pop-upU/I, on the other hand, since the every page of the multi-pagemenu is displayed in response to a user operation, all pages are deletedwhen the user_time_out_duration has elapsed. The result is a state inwhich nothing is displayed (No Menu Display).

FIG. 33 shows a data structure of page information for a given page(page y) among a plurality of pages in an x-th Display Set. As indicatedto the right-hand side of FIG. 33, the page information (y) includes

i) a page_id that uniquely identifies page (y)

ii) the content of the data structure conveyed by the page information(y), including a UO_mask_table field, an in_effect field, an out_effectfield, an animation_frame_rate_code field, adefault_selected_button_id_ref field, an animation_frame_rate_codefield, a default_selected_button_id_ref field, adefault_activated_button_id_ref field, a pallete_id_ref field, andbutton information (0) (1) . . . (number of buttons-1), and

iii) a page_version_number indicating a version number of the content ofthe page information (y).

The following describes the various fields that constitute the datastructure conveyed by the page information (y).

The UO_mask_table field is a table used to permit/disallow useroperations relating to the page (y).

The in_effect field indicates a display effect that is to be reproducedat first display of the page (y). The out_effect indicates a displayeffect to be reproduced upon display completion.

The animation_frame_rate_code field describes a frame rate that is to beapplied when displaying animation in page (y).

The default_selected_button_id_ref field indicates whether buttons whosedefault state is the selected state are determined dynamically orpassively. Specifically, when the field contains 0xff, the buttons whosedefault state is the selected state are determined dynamically. In thiscase, settings values in the Player Status Register (PSR) in thereproduction device are preferentially interpreted, and the buttonsindicated in the PSR are set to the selected state. When the field doesnot contain 0xff, the buttons whose default state is the selected stateare determined statically. In this case, the button numbers stipulatedin the default_selected_button_id_ref field are written over the PSR,and the corresponding buttons are set to the selected state.

The default_activated_button_id_ref field indicates buttonsautomatically set in the active state when a time point indicated by theselection_time_out_pts is reached.

If the default_activated_button_id_ref field contains FF, the button inthe selected state for the predetermined period is automaticallyselected. If the default_activated_button_id_ref field contains 00, thebutton in the selected state is not automatically selected. When thedefault_activated_button_id_ref field contains a value other than 00 orFF, the value is interpreted as an effective button number

The pallete_id_ref field indicates the id of the palette to be set inthe CLUT unit for the page (y)

The button information (button_info field) defines each button displayedon the page (y). The above-described fields specify the contents of eachpage in the multi-page menu.

The page_version_number field indicates a version of the contentconveyed by the page information (y) in an Epoch. Since thepage_version_number field is a main feature of the current presentinvention, a detailed description is provided below. The version of pageinformation (y) indicates a number of updates implemented on the contentof the data structure conveyed by the page information. The datastructure of page information (y) is said to have been updated if thereare one more changes in the values contained in the fields after thepage_version_number field.

The version indicated by the page_version_number field is expressedusing a serial number in a single Epoch. As a result, the valuecontained in the page_version_number field varies according to theDisplay Set that holds the page information in the Epoch. During theEpoch, the page_version_number field in the page information belongingto the Epoch Start Display Set is set to an initial value (=0). From thesecond Display Set in the Epoch onwards, the page_version_number fieldsbelonging to the Display Sets that permit updates (i.e. AcquisitionPoint-type and Normal Case-type Display Sets) are each set to a valueindicating a number of updates.

The following describes the page_version_number in detail with referenceto a specific example shown in FIG. 34. FIG. 34 shows settings for thepage_version_number field in two consecutive Display Sets (DSx+1, DSx).DSx+1 is an Acquisition Point-type Display Set, and FIG. 34 showsarbitrary page information (y) in this Display Set. When the content ofthe page information (y) of DSx+1 is identical to that of DSx, thepage_version_number field of the page information (y) in DSx+1 is set tothe same value as the page_version_number fields in the page information(y) in DSx. By referring to these page_version_number fields, thereproduction device is able to judge that the content of pageinformation (y) has not altered between the DSx and the DSx+1.Contrastingly, in FIG. 35 the content of the page information (y) in theDSx+1 differs to that in the page information (y) of the DSx. In thiscase, the value (=A+1) contained in the page_version_number field of theDSx+1 is incremented by one from that contained in the page information(y) of the DSx. The reproduction device is therefore able to discoverwhether the page information (y) in the DSx+1 has altered from the pageinformation (y) in the DSx.

FIG. 36 shows a page composed of page information (y) in the Dsx andPage information (y) in the DSx+1 for comparison.

The page constituted by the page information (y) in the DSx+1 has threebuttons (A, B and C) disposed in an order: B, C, A.

On the other hand, the page constituted by the page information (y) inthe DSx+1 has the three buttons (A, B and C) disposed in an order: A, B,C. The only difference between the two pages is that the order ofappearance of the buttons, which alters from A, B, C to B, C, A. Even inthe case of such small variations, however, the value contained in thepage_version_number field in the page information (y) of the DSx+1 willincrement. By setting the page_version_number field in this way, it ispossible to signal to the reproduction device the existence of smallchanges in the page information (y).

The above description gives an example of an Acquisition Point-typeDisplay Set in the interactive_composition. Note, however, that there isa page_version_number field in each piece of page information in theNormal Case-type Display Sets in the interactive_composition. Moreover,the page_version_number field can be made to indicate that content hasaltered between pages.

As in the first embodiment, when a preceding AV Clip and a following AVClip satisfy the three conditions, the Epoch Continue-type Display Setcan be treated as an Acquisition Point-type Display Set. Moreover, inthe Acquisition Point-type Display Set it is possible to increment thepage_version_number in each piece of page information. Thus, among thepieces of page information in the ICS, which is stored in thecomposition buffer 16 and to which the Epoch Continue-type Display Setbelongs, it is possible to limit updating to those pieces of pageinformation whose page_version_number fields have increased.

The above description relates to an improvement over the prior art inthe recording medium of the third embodiment. The following describesthe reproduction device of the third embodiment. Since theabove-described IG stream is constituted in the same way as the PGstream, playback to the IG stream can be performed using thereproduction device having the internal structure shown in FIG. 24.

The Epoch Continue-type Display Set exists in the IG stream, and thegraphics controller 17 of the third embodiment therefore performsprocessing in accordance with the flow chart of FIG. 37. This flow chartis the flow chart of FIG. 25 but with the letters ICS substituted forthe letters PCS. Besides this substitution, the flow chart of FIG. 37has additional steps of Step S21 and Step S22. Step S21 is executed inthe case that the judgments of both Step S7 and Step S8 are bothaffirmative and segmentK is to be treated as an acquisition point. InStep S21, the reproduction device judges whether or not page informationhaving an altered page_version_number exists, and if judging in theaffirmative, exchanges the corresponding page in theinteractive_composition in the composition buffer 16 for a new page. Itis thereby possible to update each piece of page information in theEpoch Continue-type Display Sets.

According to the third embodiment described above, Epoch Continue-typeDisplay Sets are present among the Display Sets used to realize thedisplay of menus, and it is therefore possible to perform consecutiveplayback of two AV Clips without breaks occurring.

Fourth Embodiment

The fourth embodiment relates the manufacturing process of the BD-ROM.FIG. 38 is a flow chart showing the manufacturing process for producingthe BD-ROM described in the first to third embodiments.

The BD-ROM manufacturing process includes a material production processS201 in which material is produced by methods such as recording movingpictures and sound, an authoring process S202 in which the material isformatted to an application format using an authoring machine, and apressing process 5203 to complete the BD-ROM through production of amaster disk and pressing/sticking.

The authoring process for the target D-ROM further includes the StepsS204 to S213, which are described below.

The following describes Steps S204 to S213. In Step S204 controlinformation, palette definition information, and graphics are described.In Step S205, the control information, the palette information, and thegraphics are converted to functional segments. In Step S206, the ICS andPTS are set based on a playback timing of a picture that is to besynchronous. In Step S207, DTS[ODS] and PTS[ODS] are set based on avalue of PTS[ICS]. In Step S208 DTS[ICS] and PTS[PDS] are set based on avalue of DTS[ODS].

In Step S209 occupancy of each of the buffers in the player is plottedagainst time. In Step S210, it is judged whether or not the plottedtransitions stay within constraints of the player model. If the judgmentis in the negative, each functional segment is overwritten in Step S211.If the judgment is in the affirmative, a Graphics Stream is generated inStep S212, and the graphics stream is multiplexed with a video streamand an audio stream to form an AV Clip in Step S213. The AV Clip is thenadapted to the BD-ROM format to complete the application format.

Modifications

Though the present present invention has been described by way of theabove embodiments, the present present invention is not limited to such.The present present invention can be realized with any of themodifications (A) to (L) below. The present invention of the claims ofthis application includes extension and generalization of the aboveembodiments and their modifications below. The degree of extension andgeneralization included is based on the state of the art in thetechnical field of the present invention at time of application.

(A) The above embodiments relate to the case where BD-ROM is used as therecording medium. The main features of the present invention, however,are to be found in the Graphics Stream recorded on the recording mediumand are not dependent on the physical characteristics of BD-ROMs.Therefore, the present invention is applicable to any recording mediumable to record a graphics stream. Examples of such a recording mediuminclude: an optical disk such as a DVD-ROM, a DVD-RAM, a DVD-RAM, aDVD-RW, a DVD-R, a DVD+RW, a DVD+R, a CR-R or a CD-RW; a magneto-opticaldisk such as a PD or an MO; a semiconductor memory card such as aCompactFlash card, a SmartMedia card, a Memory Stick card, aMultiMediaCard, or a PCM-CIA card; a magnetic disk such as a flexibledisk, SuperDisk, Zip or Clik!; a removable hard disk drive such as ORB,Jaz, SparQ, SyJet, EZFley, of Microdrive; a nonremovable hard diskdrive.

(B) The above embodiments describe the case where the reproductiondevice decodes an AV Clip recorded on the BD-ROM and output the decodedAV Clip to the television. As an alternative, the reproduction devicemay only have a BD drive with the remaining construction elements beingprovided in the television. In this case, the reproduction device andthe television can be incorporated into a home network using an IEEE1394 connector. Moreover, though the above embodiments describe the casewhere the reproduction device is connected to the television, thereproduction device may instead be integrated with a display device.Also, the reproduction device of the any of the embodiments may containonly the system LSI (integrated circuit) that performs essentialprocessing. The above described reproduction devices and integratedcircuits are all within the scope of the present invention described inthis specification. Thus any act of manufacturing a reproduction devicebased on the internal construction of the reproduction device describedin the embodiments is an act of implementing the present invention.Moreover, any act of assigning a charge (i.e. selling), giving, leasing,and/or importing the reproduction device is an act of implementing thepresent invention.

Since information processing using the programs shown in the flowchartsrealized using hardware resources, the programs describing the operationprocedures shown in the flow charts by themselves constitute an presentinvention. The above embodiments describe the case where the programsare incorporated with in the reproduction apparatus, but the programscan be implemented separately from the reproduction device as describedin the first embodiment. Acts of implementing the programs include (1)an act of producing, (2) an act of assigning with or without charge, (3)an act of leasing, (4) an act of importing, (5) an act of providing tothe public via a bi-directional electronic communications network, and(6) an act of offering for assignment or lease for storefront displays,catalogs, or brochures.

Executed in series, the steps in the flow charts can be regarded as thenecessary elements of the present present invention. Thus, the procedureshown by these flow charts discloses a form of use of the playbackmethod. If the processing of the steps shown in any of the flow-chartsis performed in sequence so as to achieve the intended aim and intendedeffect of the present invention, this clearly constitutes animplementation of the recording method of the present invention.

(E) When used in a home network interconnected via IEEE 1394, thereproduction device may transmit an Aligned Unit using the followingprocessing. The reproduction device removes a TP_extra_header from eachof the 32 EX TS packets in the aligned unit encrypts the body of each TSpacket according to the DTCP Specification, and outputs the encrypted TSpackets. When outputting the TS packets, the reproduction device insertsan isochronous packet between adjacent TS packets. The insertionposition determined based on a time indicated by an arrival_time_stampin TP_extra_header. The reproduction device outputs a DCTP_descriptortogether with the output packets. The DCTP_descriptor corresponds to acopy permission indicator in the TP_extra_header. When the reproductiondevice is used in a home network interconnected via IEEE 1394 and theDCTP_descriptor indicates “copying prohibited”, the TS cannot berecorded to other devices.

(F) The digital streams of the above embodiments are AV Clips in theBlu-ray Disk Read-Only Format, but the present present invention canalso be realized using a VOB (Video Object) of the DVD-video Format, orthe DVD-Video Recording Format. The VOB is a recording stream thatcomplies with the ISO/IEC13818-1 Standard and is obtained bymultiplexing a video stream and an audio stream. Also, the video streamin the AV Clip may be an MPEG 4 video stream or a WMV video stream.Further, the audio stream in the AV Clip may be a Linear PCM audiostream, a Dolby AC-3 audio stream, an MP3 audios stream, an MPEG-AACaudio stream, or a dts audio stream.

(G) The movie described in the above embodiments may be obtained byencoding an analog image signal that has been broadcast using analogbroadcasting techniques. Alternatively, the movie may be stream datamade up of a transport stream that has been broadcast using digitalbroadcasting techniques.

An analog/digital image signal recorded on videotape may be encoded toobtain content. An analog/digital image signal directly captured by avideo camera may be encoded to obtain content. Another possibility isthat the content is a digital work distributed by a distribution server.

(H) The Graphics Objects described in the above embodiments isrun-length encoded raster data. The reason that run-length encoding isused to compress/encode Graphics Objects is that run-length encoding issuitable for the compression and decompression of subtitles. One of theproperties of subtitles is that a relatively large number pixels havingthe same pixel value are aligned in the horizontal direction. Due tothis property, it is possible to obtain a high compression ratio whencompression is carried out using run length encoding. Moreover, sincethe decompression load is light, and the processing to decode thecompressed data is suitable for a software implementation. In the deviceused to realize the decoding, the same compression/decompression methodis used for the Graphics Object as for the subtitles. Note however, thatthe use of run length encoding on the Graphics Object is not essentialto the present invention. For instance, the Graphics Objects may be PNGdata, vector data or transparent parents.

(I) The transmission rate Rc may be set so that clearing of the graphicsplane and rendering are completed within a vertical blanking time. Ifthe vertical blanking time is set to 25% of 1/29.93 seconds, the Rc willbe 1 Gps. This way of setting Rc enables graphics to be displayedsmoothly, and is very effective in practice.

In addition to taking place within the vertical blanking time, thewriting can be synchronized with a line scan. This enables the subtitlesto be displayed smoothly with Rc=256 Mps

(J) The reproduction device in the above embodiments includes a graphicsplane. However, a line buffer that stores the uncompressed pixels of oneline may be used in place of the graphics plane. Conversion to an imagesignal is possible using the line the buffer since such conversions areperformed one line at a time.

(K) The graphics plane in the above embodiments is preferably made up ofa double buffer. In the case that graphics plane is made up of a doublebuffer, it is possible to switch between screens instantaneously, evenwhen graphics having a large data size are written to the graphics planeover a period of a number of frames. The inclusion or lack of the doublebuffer is therefore significant if full screen menus are to bedisplayed.

Three conditions are described for a Display Set (DSm+1) to be treatedas an Acquisition Point. First, the Display Set (DSm+1), which directlyfollows the AV Clip boundary; must be of the Epoch Continue-type(Condition 1). Second, the composition_number contained in the PCSbelonging to the DSm+1 must be identical to the composition_numbercontained in a directly preceding Display Set DSm (Condition 2). Third,playback of the preceding AV Clip and playback of the following AV Clipmust be seamlessly connected. However, the second and third of theseconditions are not necessary conditions. Provided that the firstcondition is satisfied (i.e. the Display Set (DSm+1) that immediatelyfollows the AV Clip boundary is of the Epoch Continue type), the DisplaySet DSm+1 can be treated as an Acquisition Point.

INDUSTRIAL APPLICABILITY

The recording medium and reproduction device of the present inventioncan be used as part of a home theater system or the like. However sincethe above embodiments disclose internal constructions of recordingmedium and reproduction device of the present invention, and the andmass production is possible based on the disclosed internalconstructions, the recording medium and the reproduction device are ofindustrial use. In other words, the recording medium and thereproduction device have industrial applicability.

1. A reproduction device for playing back one or more digital streamseach generated by multiplexing a video stream and a graphics stream, thereproduction device comprising: a video decoder operable to decode thevideo stream to obtain a moving picture; and a graphics decoder operableto decode the graphics stream to obtain a graphics object to be overlaidon the moving picture, wherein the graphics stream includes statusinformation, the graphics decoder includes a plurality of memories and acontroller, and starts managing each of the plurality of memories when adigital stream is played back, and, if a graphics stream included in thedigital stream is decoded, a graphics object obtained by decoding thegraphics stream is stored in each of the plurality of memories, thecontroller performs control over reading of the graphics object storedin each of the plurality of memories and displaying of the read graphicsobject, when two digital streams are to be played back consecutively, agraphics object included in a preceding digital stream is stored in eachof the plurality of memories, when the status information of a graphicsstream included in a succeeding digital stream shows a predeterminedtype, the controller performs control to maintain the graphics objectstored in each of the plurality of memories.
 2. A recording method forrecording one or more digital streams each generated by multiplexing avideo stream and a graphics stream, wherein the video stream constitutesa moving picture, the graphics stream constitutes a graphics object tobe overlaid on the moving picture, and the recording method comprising:generating the video stream, generating the graphics stream, generatinga digital stream by multiplexing the video stream and the graphicsstream, recording the digital stream on a recording medium, and saidgraphics stream generating comprising: if two digital streams are to beplayed back consecutively, generating status information indicating thata graphics object included in a preceding digital stream is to bemaintained in a memory of a reproduction device for a succeeding digitalstream, and the graphics stream including the status information isgenerated in said graphics stream generating.
 3. The recording method ofclaim 2 further comprising: recording playback path information thatindicates a playback path for each digital stream, and if two digitalstreams are to be played back consecutively, the playback pathinformation includes a seamless flag that indicates whether or notmoving picture playback is to be seamless, and the status information ispermitted to be used only if the moving picture playback is to beseamless.
 4. A playback method for playing back one or more digitalstreams each generated by multiplexing a video stream and a graphicsstream, the playback method comprising: decoding the video stream toobtain a moving picture, and decoding the graphics stream to obtain agraphics object to be overlaid on the moving picture, and the graphicsstream includes status information, a computer includes a plurality ofmemories, said graphics object obtaining starts managing each of theplurality of memories when a digital stream is played back, and, if agraphics stream included in the digital stream is decoded, a graphicsobject obtained by decoding the graphics stream is stored in each of theplurality of memories, said graphics object obtaining performs controlover reading of the graphics object stored in each of the plurality ofmemories and displaying of the read graphics object, when two digitalstreams are to be played back consecutively, a graphics object includedin a preceding digital stream is stored in each of the plurality ofmemories, when the status information of a graphics stream included in asucceeding digital stream shows a predetermined type, said graphicsobject obtaining performs control to maintain the graphics object storedin each of the plurality of memories.